Permanent magnet type dynamo-electric machine and permanent magnet synchronous generator for wind power generation

ABSTRACT

The present invention has been made for the purpose of obtaining a permanent magnet type dynamo electric machine, and a permanent magnet type synchronous generator for wind power generation, each of which is capable of reducing an eddy current loss of a rotor while having a construction of an integral one-piece rotor yoke.  
     Each of the generators is constructed in such a way that it includes a rotor  100  having a plurality of magnetic poles composed of permanent magnets  4 , and a stator  101  having armature windings concentratedly wound around teeth, and when the number of pole pairs of the magnetic poles of the rotor  100  is P, a diameter of the rotor  100  is D[m], and a spatial harmonic order of a predetermined harmonic component of an armature magnetomotive force of the rotor  100  is N (a mechanical angle 360 degrees is decided as 1-st order), the P, D and N meet a relationship of ((N+P) to the 1.5-th power)×N to the minus 4-th power)×(the square of P)×D&lt;0.6 (its unit is m).

TECHNICAL FIELD

[0001] The present invention relates to a permanent magnet type dynamoelectric machine, and a permanent magnet type synchronous generator forwind power generation, and more particularly, to a permanent magnet typedynamo electric machine, and a permanent magnet type synchronousgenerator for wind power generation, each including a rotor having aplurality of magnetic poles composed of permanent magnets, and a statorhaving armature windings wound around the magnetic poles.

BACKGROUND ART

[0002] Heretofore, a so-called permanent magnet type dynamo electricmachine with concentrated winding including a rotor having a pluralityof magnetic poles composed of permanent magnets, and a stator havingarmature windings concentratedly wound around the magnetic poles hasbeen used in various applications. The concentrated winding has theconstruction in which the armature windings are concentratedly woundaround the magnetic poles of the stator and hence automatic winding by amachine is possible therefor. Thus, many permanent magnet type dynamoelectric machines with concentrated winding are used mainly for smallmotors such as servo. In such a small motor, a copper loss, a core loss,and a mechanical loss occupy a majority of the losses, and therefore aneddy current loss caused in the rotor does not become a problem in mostcases.

[0003] On the other hand, in a large generator whose power generationexceeds several kilowatts, distributed winding was used in many cases inthe past. However, the need for the concentrated winding having a smallcoil end is increasing even in a large generator. For example, in thecase where a permanent magnet type synchronous generator is adopted in awind power generation system, in particular, a gearless type wind powergeneration system, it can be said that the selection of the concentratedwinding is better from a viewpoint that as compared with the distributedwinding, in the concentrated winding, a small coil end allows an axiallength to be reduced, and moreover, a less copper loss caused inarmature windings enables to realize a high efficiency promotion.

[0004] As described above, the concentrated winding has a superioradvantage in that the coil end is small, and moreover, the automaticwinding is possible. However, it has a problem in that an eddy currentloss of a rotor due to a magnetomotive force of an armature currentbecomes larger than that in the distributed winding. Moreover, in recentyears, high performance magnets such as a rare earth magnet, each havinga high residual magnetic flux density and a high coercive force, havebeen positively utilized as magnetic poles of a rotor of a largecapacity generator. For example, an Nd—Fe—B-based magnet has suchcharacteristics as being high in its electric conductivity, therebyallowing an eddy to easily flow as compared with a ferrite-based magnet.

[0005] From the above-mentioned reasons, in the large capacity generatorwith the concentrated winding, in particular, in the permanent magnettype dynamo electric machine, and the permanent magnet type synchronousgenerator for wind power generation, each having a rotor with a diameterlarger than 1 m, the eddy current loss caused in the rotor reaches asignificant level in some cases. Hence, such problems arose that theefficiency of the rotor was remarkably reduced due to the eddy currentloss and that a temperature of the rotor rose due to the eddy currentloss, incurring the demagnetization of the magnet. In addition, even ifthe demagnetization was not incurred, the residual magnetic flux densitywas reduced due to the temperature rise, with the result that themagnetic flux generated by the magnets was reduced. For this reason,more armature current needs to be caused to flow in order to generatethe same output power as that in a state free from the temperature rise,and hence there was also a problem in that a copper loss is increasedand the efficiency is reduced.

[0006] As a method for solving such problems, conventionally, there is amethod in which a yoke of the rotor is constructed by a laminated steelplate to thereby reduce the eddy current. In addition, in JP 2001-54271A, there is disclosed a method in which an iron core of a rotor isconstructed by a massive yoke instead of a laminated steel plate, andthe yoke is partitioned so that a path of the eddy current is cut off,to thereby reduce the eddy current.

[0007] However, there is a problem in that if the lamination structureis adopted for a yoke of a rotor, the cost becomes higher than in thecase where an iron core is made of a massive yoke. Moreover, if amassive yoke is partitioned as disclosed in JP 2001-54271 A above, therearise various problems as will be described below. For example, due toan increase in the processing cost, the cost becomes higher as comparedwith an integral one-piece massive yoke. In addition, in the case wherefluctuation occurs in thicknesses of insulating portions provided to theyoke of a rotor, fluctuation also occurs in the flux densities in gapportions of a motor. Thus, there is a fear in that this leads toununiformity of the electromagnetic force which causes noises andvibration. In addition, there is a problem in that insulating portionsfor electrically insulating and dividing the yoke are provided in orderto partition the yoke, and hence the magnetomotive force is consumedtherein, which leads to reduction of the output power of the dynamoelectric machine.

[0008] As described above, in the conventional permanent magnet typedynamo electric machine, the conventional permanent magnet typesynchronous generator for wind power generation, and the like, in orderto reduce the eddy current, the construction in which a laminationstructure is adopted for a yoke of a rotor and the construction in whicha massive yoke is partitioned have been proposed. However, when thelamination structure is adopted, there is a problem in that the costbecomes higher due to the increase in the processing cost. On the otherhand, when a massive yoke is partitioned, there arises a problem in thatfluctuation occurs in the magnetic flux densities of gap portions of amotor, which leads to ununiformity of the electromagnetic force.Consequently, it can be said that the yoke of the rotor is desirably ofan integral type.

[0009] The present invention has been made in order to solve theabove-mentioned problems associated with the prior art, and it is,therefore, an object of the present invention to obtain a permanentmagnet type dynamo electric machine, and a permanent magnet typesynchronous generator for wind power generation, each being capable ofreducing an eddy current loss of a rotor, while keeping a constructionof an integral type for a rotor yoke.

DISCLOSURE OF THE INVENTION

[0010] The present invention relates to a permanent magnet type dynamoelectric machine and to a permanent magnet type synchronous generatorfor wind power generation, each of which includes a rotor having aplurality of magnetic poles composed of permanent magnets, and a statorhaving armature windings concentratedly wound around teeth, in whichwhen the number of pole pairs of the rotor is P, a diameter of the rotoris D[m], a spatial harmonic order of a predetermined harmonic componentof an armature magnetomotive force of the rotor is N (a mechanical angle360 degrees is decided as 1-st order), and an output of the permanentmagnet type dynamo electric machine is P_(out), and then the D is madeequal to or larger than 0.00045 P_(out)+1.2, a parameter X (its unit ism) used to evaluate the rate of an eddy current loss caused in the rotoris defined as follows;

X=(N+P)^(1.5) N ⁻⁴ P ² D

[0011] and values of the P, D and N are selected so that a value of theX becomes smaller than a predetermined value.

[0012] Further, the present invention relates to a permanent magnet typedynamo electric machine and to a permanent magnet type synchronousgenerator for wind power generation, each of which includes a rotorhaving a plurality of magnetic poles composed of permanent magnets, anda stator having armature windings concentratedly wound around teeth, inwhich when the number of pole pairs of the rotor is P, a diameter of therotor is D[m], a spatial harmonic order of a predetermined harmoniccomponent of an armature magnetomotive force of the rotor is N (amechanical angle 360 degrees is decided as 1-st order), and an output ofthe permanent magnet type dynamo electric machine is P_(out), and thenthe D is made equal to or larger than 0.00045 P_(out)+1.2, the P, D andN meet the following relationship:

(N+P)^(1.5) N ⁻⁴ P ² D<0.6

[0013] (its unit is m).

[0014] Further, when the number of slots of the stator is S, the P andthe S meet a relationship of 2 P<S.

[0015] Further, when the number of slots of the stator is S, the P andthe S meet a relationship of 2 P:S=2:3, and also the P and the D meetthe following relationship:

P ^(−0.5) D<1.85

[0016] (its unit is m).

[0017] Further, when the number of slots of the stator is S, the P andthe S meet a relationship of 2 P:S=8:9, and also the P and the D meetthe following relationship:

P ^(−0.5) D<0.43

[0018] (its unit is m).

[0019] Further, when the number of slots of the stator is S, the P andthe S meet a relationship of 2 P:S=10:12, and also the P and the D meetthe following relationship:

P ^(−0.5) D<0.62

[0020] (its unit is m).

[0021] Further, the permanent magnet constituting the magnetic poles ofthe rotor is axially divided to provide a partition construction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a cross sectional view showing a construction of apermanent magnet type synchronous generator according to an embodimentmode 1 of the present invention;

[0023] FIGS. 2 show an armature magnetomotive force in the permanentmagnet type synchronous generator according to the embodiment mode 1 ofthe present invention;

[0024]FIG. 3 is a graph showing the results of the Fourier analysis of amagnetomotive force waveform (when the number of poles: the number ofslots is 2:3) in the permanent magnet type synchronous generatoraccording to the embodiment mode 1 of the present invention;

[0025]FIG. 4 shows a change of a magnetic flux with elapse of time and apath of an eddy current caused to flow through a rotor in the permanentmagnet type synchronous generator according to the embodiment mode 1 ofthe present invention;

[0026]FIG. 5 is a graph showing the results of the Fourier analysis of amagnetomotive force waveform (when the number of poles: the number ofslots is 4:3) in the permanent magnet type synchronous generatoraccording to the embodiment mode 1 of the present invention;

[0027]FIG. 6 is a graph showing the results of the Fourier analysis of amagnetomotive force waveform (when the number of poles: the number ofslots is 10:9) in the permanent magnet type synchronous generatoraccording to the embodiment model of the present invention;

[0028]FIG. 7 is a graph showing the results of the Fourier analysis of amagnetomotive force waveform (when the number of poles: the number ofslots is 8:9) in the permanent magnet type synchronous generatoraccording to the embodiment mode 1 of the present invention;

[0029]FIG. 8 is a graph showing the results of the Fourier analysis of amagnetomotive force waveform (when the number of poles: the number ofslots is 10:12) in the permanent magnet type synchronous generatoraccording to the embodiment mode 1 of the present invention;

[0030]FIG. 9 shows an example of specifications of the permanent magnettype synchronous generator according to the embodiment mode 1 of thepresent invention;

[0031]FIG. 10 is a graph showing a change of the ratio of a parameter Xto an eddy current loss in the permanent magnet type synchronousgenerator according to the embodiment model of the present invention;

[0032]FIG. 11 is a view showing a construction of a wind powergeneration system according to an embodiment mode 2 of the presentinvention;

[0033]FIG. 12 is a view showing a construction of another example of awind power generation system according to the embodiment mode 2 of thepresent invention;

[0034]FIG. 13 is a graph showing a relationship of a ratio of an eddycurrent loss v.s. combinations of the number of poles and the number ofslots in a permanent magnet type generator according to an embodimentmode 3 of the present invention;

[0035]FIG. 14 is a graph showing a relationship of a ratio of an eddycurrent loss v.s. (the number of slots/the number of poles) in thepermanent magnet type generator according to the embodiment mode 3 ofthe present invention;

[0036]FIG. 15 is a partial perspective view showing a construction of apermanent magnet type synchronous generator according to an embodimentmode 4 of the present invention; and

[0037]FIG. 16 is a graph showing a relationship between an output of agenerator and a rotor outer diameter in the permanent magnet typesynchronous generator according to the embodiment mode 1 of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION EMBODIMENT 1

[0038] An example of an embodiment mode 1 of the present invention isshown in FIG. 1. FIG. 1 is a permanent magnet type synchronous generatorof an inner rotor type. That is, in FIG. 1, a stator 101 is positionedoutside a rotor 100. In FIG. 1, reference numeral 1 designates a statoriron core constituting the stator 101, reference numeral 2 designates aplurality of teeth provided in the stator iron core 1, reference numeral3 designates a slot as a recess portion which is formed between theadjacent teeth 2, reference numeral 4 designates a plurality ofpermanent magnets provided in the rotor 100, reference numeral 5designates an integral type massive rotor yoke to which the permanentmagnets 4 are attached at equal intervals, and reference numeral 6designates a rotation axis of the rotor 100.

[0039] As shown in FIG. 1, a rotor outer diameter is 3 m, the number ofpermanent magnets 4 provided in the rotor 100 (i.e., the number of rotormagnetic poles) is 64, and each of the number of teeth 2 of the stator101 and the number of slots 3 of the stator 101 is 96. A surface magnettype synchronous generator is shown, in which the permanent magnets 4are arranged on the surface of the massive yoke 5 of the rotor 100, andthe stator 101 has the 96 teeth 2. While the illustration is omitted inFIG. 1, a winding system of a so-called concentrated winding is adopted,in which armature wirings are concentratedly wound around the teeth 2.

[0040]FIG. 2(a) schematically shows a part of the stator 101 and therotor 100 of FIG. 1, and FIGS. 2(b), (c) and (d) show magnetomotiveforce waveforms each of which is formed by an armature current. In FIG.2, reference numeral 8 designates the armature windings wound around theteeth 2. Since other constructions correspond to those shown in FIG. 1,the same constituent elements are designated with the same referencenumerals, and the descriptions thereof are omitted here. Since in thisembodiment mode, the ratio of the number of poles of the rotor 100 tothe number of slots of the stator 101 is 2:3, the 2 poles and 3 slotselectromagnetically become one unit. Thus, considerations with respectto the 2 poles and 3 slots may only be made. In the stator 101, as shownin FIG. 2(a), the armature wirings 8 of a phase U, a phase V and a phaseW, i.e., 3 phases in total are accommodated in the slots 3, and thesearmature windings 8 are concentratedly wound around the teeth 2.Sine-wave like currents whose electrical angles are shifted by 120degrees with one another, are caused to flow through the armaturewindings 8 of 3 phases, respectively. At the time when the currents havebeen caused to flow through the armature windings 8, respectively, insuch a manner, a magnetomotive force having a rectangular waveform isgenerated in each gap portion. For example, when a current of 1 iscaused to flow through the armature winding of the phase U, currents of−½ are caused to flow through the armature windings of the phase V andthe phase W, respectively. At this time, the waveform of themagnetomotive force generated in each gap portion is as shown in FIG.2(b). Actually, since the currents of the 3 phases are changed with timein accordance with a sine wave shape, the waveform of this magnetomotiveforce is also changed. If the waveform of the magnetomotive force isdeveloped in the form of Fourier series with respect to time and space,it is understood that there are magnetomotive force componentssynchronous with the rotor 100, and asynchronous components.

[0041] The results of developing the magnetomotive force in terms of theFourier series are shown in FIG. 3. FIG. 3 shows the results of theFourier analysis of the magnetomotive force of the stator when the ratioof the number 2 P of poles to the number S of slots is 2:3. The axis ofabscissa represents a spatial harmonic order with the 2 poles (itselectrical angle is 360 degrees) as a fundamental wave. Then, when itssign is positive, the axis of abscissa represents a magnetomotive forcewhich shows a positive-phase and which is rotated in the same directionas that of the rotor 100. On the other hand, when its sign is negative,the axis of abscissa represents a magnetomotive force which shows anopposite phase and which is rotated in a direction opposite to therotational direction of the rotor 100. The axis of ordinate representsamplitude of a magnetomotive force of a component concerned. Then, thenormalization is carried out with magnitude of a component synchronouswith the rotor, i.e., +1-st order as 1. However, all the harmoniccomponents are not shown, and hence the components of equal to or higherthan 15-th orders are omitted. Of the components of the magnetomotiveforce, the component synchronous with the magnetic poles of the rotor100 is the component of +1-th order on the axis of abscissa, and atorque is obtained by this component. In addition, since thismagnetomotive force component is the magnetomotive force which is notchanged with time when viewed from the coordinate system fixed to therotor 100, it does not become a cause of generation of an eddy currentof the rotor 100. On the other hand, since the components other thanthat magnetomotive force component are the asynchronous components andhence are changed with time when viewed from the coordinate system fixedto the rotor 100, they become the cause of an eddy current of the rotor100. In addition, of those asynchronous components, the component of−2-nd order has the largest amplitude. The synchronous component (thepositive-phase component of a fundamental wave) and the opposite-phasecomponent of 2-nd order as an example of the asynchronous component areshown in FIGS. 2(c) and 2(d), respectively. As has already beendescribed, this synchronous component does not become the cause of aneddy current, while the asynchronous components cause an eddy current inthe rotor 100. In particular, when the ratio of the number of poles tothe number of slots is 2:3 as described above, since of theopposite-phase components, the opposite-phase component of 2-nd orderhas the largest amplitude, it may safely be said that the opposite-phasecomponent of 2-nd order is the main cause of an eddy current loss causedin the rotor 100. Since the number of poles of the generator handled inthis embodiment mode is 64, a spatial harmonic order of a waveform ofthe magnetomotive force becoming the main cause of the eddy currentbecomes 64-th order if a mechanical angle of 360 degrees are assumed tobe 1-st order.

[0042] Next, for the purpose of grasping an eddy current of the rotor100 generated by the presence of the above-mentioned asynchronouscomponents, an eddy current will now be derived approximately using asimple model. Moreover, let us consider what relationship is establishedamong the order N of the asynchronous component of the magnetomotiveforce to be the cause of the eddy current concerned, the number P ofpole pairs of the rotor 100 and an outer diameter D[m] of the rotor 100,and in what manner the above-mentioned N and P should be selected inorder to reduce the eddy current.

[0043] An upper stage of FIG. 4 shows a change with elapse of time of amagnetic flux generated with the asynchronous components of themagnetomotive force to be the cause of an eddy current. In addition, alower stage of FIG. 4 shows a minute circuit (slant line portion) whichis used when a path of an eddy current caused to flow through the rotor100 due to a change of the magnet flux and an eddy current loss areobtained, and also shows a situation when the rotor 100 is overlookedfrom a gap surface in a simplified manner. Note that, in FIG. 4,reference symbol w[m] designates a length for one period of amagnetomotive force to be the cause of an eddy current, i.e., awavelength, and reference symbol L[m] designates a core length of thegenerator. In addition, reference symbol x designates a coordinate [m]representing a circumferential position, and reference symbol ydesignates a coordinate [m] representing an axial position. The pathalong which an eddy current is caused to flow, as shown in FIG. 4, isformed within a range of a width for a half wavelength of amagnetomotive force, i.e., a width of w/2. Then, a minute circuit isconsidered in the position, as exhibited by a slant line portion of thefigure within the range of w/2, defined by the circumferential width 2xand the axial width 2y, and an eddy current loss is obtained from aresistance of this minute circuit and a magnetomotive force applied tothis circuit to be further spatially integrated to thereby calculate theeddy current loss caused in the whole generator.

[0044] First of all, a resistance r[Ω] of the minute circuit isobtained. Since the resistance r is in proportion to resistivity ρ [Ωm]and a length of the circuit, and is inversely proportional to a crosssection of the circuit, it is expressed as follows:

r=ρ(4y/δdx+4x/δdy) tm (1)

[0045] However, here, δ is a skin depth of an eddy current and its unitis m. From FIG. 4, the following Expression is geometricallyestablished: $\begin{matrix}{{y = {\frac{L}{w}x}},{{dy} = {\frac{L}{w}{{dx}.}}}} & (2)\end{matrix}$

[0046] When Expression (2) is substituted for Expression (1), thefollowing Expression is obtained: $\begin{matrix}{r = {\frac{4\rho}{\delta}\frac{L^{2} + w^{2}}{wL}{\frac{x}{dx}.}}} & (3)\end{matrix}$

[0047] Next, an electromotive force applied to this minute circuit isobtained. A temporal and spatial change of the asynchronous component ofthe magnetic flux to be the cause of an eddy current is expressed asfollows: $\begin{matrix}{{B\left( {x,t} \right)} = {B\quad {{\sin \left( {{\frac{2\pi}{w}x} - {\omega \quad t}} \right)}.}}} & (4)\end{matrix}$

[0048] This Expression shows that a spatial frequency of a change of themagnetic flux density is 2n/w, and a frequency thereof is ω [rad/sec].Since the electromotive force applied to the minute circuit is expressedin the form of the time differential of a cross magnetic flux in aninterval [−x, x], it is expressed as follows: $\begin{matrix}{e = {{- \frac{}{t}}{\int_{- x}^{x}{{B\left( {\xi,t} \right)}2y{{\xi}.}}}}} & (5)\end{matrix}$

[0049] When Expression (4) is substituted for Expression (5), thefollowing Expression (6) is obtained. $\begin{matrix}{e = {\frac{2\quad \omega \quad {BL}}{\pi}x\quad {\sin \left( {\frac{2\quad \pi}{w}x} \right)}\cos \quad \omega \quad t}} & (6)\end{matrix}$

[0050] Since the electromotive force is changed with time in the form ofa sine wave, its effective value E is expressed as follows:$\begin{matrix}{E = {\frac{\sqrt{2}\omega \quad {BL}}{\pi}x\quad {{\sin \left( {\frac{2\pi}{w}x} \right)}.}}} & (7)\end{matrix}$

[0051] If a reactance of the minute circuit is disregarded, then an eddycurrent loss dQ[W] generated in the minute circuit can be obtained asfollows from Expressions (3) and (7): $\begin{matrix}{{dQ} = {\frac{E^{2}}{r} = {\frac{\omega^{2}B^{2}\delta}{2\quad \pi^{2}\rho}\frac{{wL}^{3}}{L^{2} + w^{2}}x\quad {{\sin^{2}\left( {\frac{2\quad \pi}{w}x} \right)}.}}}} & (8)\end{matrix}$

[0052] An eddy current loss of this minute circuit is integrated for aninterval [−w/4, w/4]. Then, since the path along which the eddy currentis caused to flow is formed by a width of a half wavelength of amagnetomotive force and hence the integrated value must be multiplied by2N (=2πD/w), an eddy current loss Q[W] for the whole rotor is expressedas follows: $\begin{matrix}\begin{matrix}{Q = {2N{\int{Q}}}} \\{= {\frac{2\quad \pi \quad D}{w}{\int_{0}^{w/4}{\frac{\omega^{2}B^{2}\delta}{2\quad \pi^{2}\rho}\frac{{wL}^{3}}{L^{2} + w^{2}}x\quad {\sin^{2}\left( {\frac{2\pi}{w}x} \right)}\quad {x}}}}} \\{= {\left( {\frac{1}{64\pi} + \frac{1}{16\pi^{3}}} \right)\frac{D\quad w^{2}B^{2}\delta}{\rho}{\frac{L^{3}w^{2}}{L^{2} + w^{2}}.}}}\end{matrix} & (9)\end{matrix}$

[0053] Moreover, when resistivity, permeability and a frequency are p, μand ω, respectively, the skin depth δ is expressed as follows:$\begin{matrix}{\delta = {\sqrt{\frac{2\rho}{\omega\mu}}.}} & (10)\end{matrix}$

[0054] Here, since normally, a relationship of w<<L is established in agenerator, the following approximate Expression can be obtained:$\frac{L^{3}w^{2}}{L^{2} + w^{2}} \approx {L\quad {w^{2}.}}$

[0055] In addition, since a relationship of w=πD/N is established, thefollowing approximate Expression (11) can be obtained from Expressions(9) and (10):

Q≈Kω ^(1.5) N ⁻² B ² D ³ L   (11)

[0056] However, K is expressed as follows: $\begin{matrix}{K = {\left( {\frac{\pi}{64} + \frac{1}{16\pi^{2}}} \right){\sqrt{\frac{2}{\mu\rho}}.}}} & (12)\end{matrix}$

[0057] In addition, if a rotational frequency ω_(m) [rad/sec] of agenerator is used, then an angular frequency w [rad/sec] of the eddycurrent generated by the asynchronous magnetomotive force of a spatialharmonic order N is expressed as follows:

ω=(N±P)ω_(m)   (13)

[0058] However, the sign “+” in Expression (13) corresponds to the casewhere the magnetomotive force of the spatial harmonic order N is of anopposite phase, while the sign “−” corresponds to the case where themagnetomotive force of the spatial harmonic order N is of apositive-phase. That is, when viewed from the coordinate system fixed tothe rotor, the frequency of the magnetomotive force advancing in anopposite direction with the rotor appears to be high, conversely thefrequency of the magnetomotive force advancing in the same direction asthat of the rotor appears to be low. Consequently, Q can be written asfollows from Expressions (11) and (13):

Q=Kω _(m) ^(1.5)(N±P)^(1.5) N ⁻² B ² D ³ L   (14),

[0059] What values the components of the magnetomotive force takeagainst the various ratios of the numbers of poles to the numbers ofslots which are usually used in the concentrated wiring are shown inFIGS. 5 to 8. FIG. 5 shows the results of the Fourier analysis of themagnetomotive force of the stator when the ratio of the number 2 P ofpoles to the number S of slots is 4:3, FIG. 6 shows the results of theFourier analysis of the magnetomotive force of the stator when the ratioof the number 2 P of poles to the number S of slots is 10:9, FIG. 7shows the results of the Fourier analysis of the magnetomotive force ofthe stator when the ratio of the number 2 P of poles to the number S ofslots is 8:9, and FIG. 8 shows the results of the Fourier analysis ofthe magnetomotive force of the stator when the ratio of the number 2 Pof poles to the number S of slots is 10:12.

[0060] In the case of the distributed winding, when 1 or 2 is obtainedevery pole and every phase, the asynchronous components of themagnetomotive force are of 5-th order in positive-phase, and of 7-thorder or more in opposite phase. Thus, they are the components of higherorder than that of the fundamental wave. However, in the case of theconcentrated wiring, it is understood that even in the case of anasynchronous component having higher order than that of the fundamentalwave, the order of the asynchronous component is near that of thefundamental wave as compared with the distributed wiring, and anasynchronous component is present even in a component having order lowerthan that of the fundamental wave in some cases. Furthermore, whenspatial harmonic order of the magnetomotive force of the asynchronouscomponent becoming the main cause of the eddy current is N (a mechanicalangle 360 degrees is 1-st order), its magnitude is in proportion to theratio of the number of pole pairs to the spatial harmonic order, i.e.,P/N. Moreover, it is also found out from FIG. 3 and FIGS. 5 to 8 that ofthe magnetomotive force, i.e., the asynchronous components becoming themain cause of the eddy current loss, the asynchronous component havingthe largest amplitude is of an opposite phase. Accordingly, Expression(14) can be rewritten as follows:

Q=K ₁ω_(m) ^(1.5)(N+P)^(1.5) N ⁻⁴ P ² D ³ L   (5)

[0061] where K₁ is a proportional constant. From the foregoing, anapproximate Expression of the eddy current loss caused in the rotorcould have been derived. This Expression shows that in a permanentmagnet type generator or motor, the eddy current loss caused in therotor greatly depends on the number P of pole pairs, the rotor outerdiameter D, and the spatial harmonic order N of the opposite-phasemagnetomotive force.

[0062] On the other hand, in general, it is known that the followingrelationship is approximately established among an outer diameter D, anaxis length L and a rotational frequency ω_(m) of a rotor, and an outputP_(out).

P _(out) =K ₂ω_(m) D ² L   (16)

[0063] where K₂ is a proportional constant. Accordingly, Expression (15)is divided by Expression (16) to thereby allow the rate of the eddycurrent loss to the output to be found. $\begin{matrix}{\frac{Q}{P_{out}} = {\frac{K_{1}}{K_{2}}{\omega_{m}^{0.5}\left( {N + P} \right)}^{1.5}N^{- 4}P^{2}D}} & (17)\end{matrix}$

[0064] The factors depending on the construction of the generator, i.e.,the number P of pole pairs, the spatial harmonic-order N of the higherharmonics of the magnetomotive force and the rotor outer diameter D aretaken out from Expression (17), and then X (its unit is m) is defined asfollows with these factors as parameters used to evaluate the rate ofthe eddy current loss caused in the rotor of the generator or motor.

X=(N+P)^(1.5) N ⁻⁴ P ² D   (18)

[0065] While X, of course, does not show the rate in the strict sense ofthe word, it is considered that X is calculated in the variousgenerators or motors to be aware of its magnitude to thereby become acriterion in accordance with which the magnitude of the eddy currentloss is judged.

[0066] In the generator, such as a gearless type wind generator,requiring a large torque by rotating the rotor at a low speed, asapparent from Expression (16), increasing the diameter D is moreadvantageous than increasing the axis length L. In addition, consideringwith respect to the ratio of the axis length L to the diameter D, in thecase where L is increased, a span of a bearing is increased, and itbecomes necessary to supplement the rigidity, which leads to an increasein weight of the generator. Moreover, in the wind power generation,there are some cases a construction is adopted in which a bearing isprovided only on one side of a generator. However, if L is increased,the mechanical rigidity is reduced, and it becomes impossible to realizethis construction. Furthermore, if L is increased, the cooling thereforbecomes impossible as long as a duct is not provided in viewpoint of theheat design. However, there is a problem in that if a duct is provided,L is further increased, and the weight is also increased. As a result ofmaking an examination in the light of the foregoing, it has been foundout that establishment of a relationship of L≦D is desirable, morepreferably, a relationship of L≦0.8 D is established, and furthermorepreferably, a relationship of L≦0.5 D is established.

[0067] The case where for a relationship of an output P_(out) of agenerator v.s. D, L=D, L=0.8D and L=0.5D are respectively set is shownin FIG. 16. It is understood that as the output is increased, D needs tobe increased. In addition, for the wind power generation, from aviewpoint of the mechanical rigidity and the heat design which havealready been described, it is desirable that the design is made so as tomeet an area above a curve in the case of L=D, it is more desirable thatthe design is made so as to meet an area above a curve in the case of L32 0.8 D, and it is furthermore desirable that the design is made so asto meet an area above a curve in the case of L=0.5 D. Accordingly, it isunderstood from FIG. 16 that when the output is 2,000 kW, the design ispreferably made so as to meet a relationship of D≧2.2 [m], morepreferably so as to meet a relationship of D≧2.3 [m], and further morepreferably so as to meet a relationship of D≧2.7 [m]. Moreover, it isunderstood that when the output is 500 kW, the design is preferably madeso as to meet a relationship of D≧1.4 [m], more preferably so as to meeta relationship of D≧1.5 [m], and further more preferably so as to meet arelationship of D≧1.8 [m]. Also, it is understood that when the outputis 100 kW, the design is preferably made so as to meet a relationship ofD≧0.7 [m], more preferably so as to meet a relationship of D≧0.8 [m],and further more preferably so as to meet a relationship of D≧0.9 [ml.Then, if an area having an output equal to or larger than 500 kW islinearly approximated, D=0.00045 P_(out)+1.2 when L=D, D=0.00048P_(out)+1.3 when L=0.8 D, and D=0.00057 P_(out)+1.5 when L=0.5 D arerespectively obtained (in these expressions, unit of P_(out) is kW, andunit of D is m). Accordingly, it is desirable that the design is made soas to meet an area in which D is larger than that of these straightlines.

[0068] When the linear approximation is made, in the range in which theoutput is small, the approximation does not meet the actual curve.However, when the realization of the generators or motors with serialcapacities is considered, the outer diameters are substantially madeidentical to one another and the axis lengths are adjusted because oflimitations of production facility and the like in many cases. From thisreason, even in an area in which the output is low, the linearapproximation is adopted so as not for an outer diameter to be abruptlydecreased. From the foregoing, since even when the output becomes low,an outer diameter is not extremely decreased, such an effect can beobtained that even in the case where the same production facility isadopted, it is possible to manufacture a generator having a low output.

[0069] In a gearless type generator for wind power generation, in thecase of the generator having such a large capacity as to exceed 100 kW,such effects can be obtained that if a relationship between the rotorouter diameter D and the axis length L, or a value of D are designed soas to meet the above-mentioned conditions, a large torque is obtained torealize the design suitable for the gearless type, and in addition,since a compact construction is obtained, the cooling performance can beensured even if no duct is provided, and so forth, and hence thisbecomes advantageous to the heat design as well. Also, such an effectcan be obtained that since a span of the bearing is shortened, themechanical rigidity can be ensured, and hence a construction alsobecomes possible in which the bearing is provided only on one side.

[0070] On the other hand, paying attention to X, when a dynamo electricmachine having a large outer diameter, in particular, a wind powergenerator having such an outer diameter as to exceed 1 m is designed, itmay safely be said that an eddy current caused to flow through a rotorcannot be ignored as long as P and N are not suitably selected.

[0071] For the purpose of verifying propriety of this parameter, sixkinds of generators were designed in accordance with six kinds ofspecifications as shown in FIG. 9, and then eddy current lossesgenerated in rotors during the rated running were obtained on the basisof the electromagnetic analysis. The results of analyzing the rate ofthe eddy current loss to the rated output in each of the specificationsare shown in the most right-hand column of FIG. 9. Moreover, a graph inwhich X is plotted on the axis of abscissa, and the rate of the eddycurrent loss to the output is plotted on the axis of ordinate is shownin FIG. 10. It is understood that the correlation is shown between therate of the eddy current loss to the output and the parameter X.

[0072] Next, let us consider in what manner X should be selected when aneddy current loss of a rotor is reduced and a high efficiency generatoror motor is designed. If the efficiency of a generator or motor isintended to be designed so as to meet equal to or higher than 95%, thenthe total of a copper loss, a core loss and a mechanical loss caused ina stator, and a stray load loss containing an eddy current loss of arotor needs to be designed so as to meet equal to or smaller than 5%.Since the mechanical loss is generally smaller than the copper loss andthe core loss, it does not need to be taken into consideration so much.Though the copper loss and the core loss can be reduced on the basis ofa size, a shape and the like of the stator to some degree, there is alimit thereto. Then, it is considered that if a construction is adoptedin which the eddy current loss of the rotor can be reduced down to ahalf of the total loss 5%, i.e., 2.5%, then the total loss of summing upthe losses such as the copper loss and the core loss can be suppressedto about 5%. In other words, it is considered that if the eddy currentloss of the rotor can be suppressed to about 2.5% of the rated output,then the high efficiency of 95% can be attained. Then, it is conceivablethat since for attaining equal to or smaller than 2.5% as the rate ofthe eddy current loss in the graph shown in FIG. 10, the value X needsto be suppressed to equal to or smaller than 0.6 [m], if the followingExpression (19) is obtained, then it is possible to realize a highefficiency permanent magnet type generator or motor. For the generatorof FIG. 1, as a result of analysis of the magnetic field, it was foundthat the eddy current loss of the rotor is no more than 0.6% of therated output. Since X is 0.17 [m] in this generator, of course, thiscondition meets Expression (19).

(N+P)^(1.5) N ⁴ P ² D<0.6   (19)

[0073] From the foregoing, such a construction as to meet Expression(19) is adopted, whereby even if a permanent magnet type dynamo electricmachine is large-sized, the spatial harmonic order N of a specificarmature magnetomotive force to be the cause of the eddy current of arotor can be made large to allow the eddy current generated in the rotorto be reduced. As a result, such an effect can be obtained that thecalorification of the rotor can be suppressed, and at the same time,such an effect can also be obtained that the high efficiency promotionof the dynamo electric machine can be realized. Furthermore, in thisembodiment mode, such an effect can be obtained that the eddy currentloss of the rotor can be reduced through the use of the massive rotoryoke, without adopting such a complicated and expensive construction asdescribed in the prior art, where a yoke of a rotor is partitioned orinsulatedly divided. In addition, in this embodiment mode, thedescription has been given with respect to the surface magnet typedynamo electric machine including magnets on the surface of the rotor.However, a buried magnet type dynamo electric machine as well havingmagnets buried in a rotor iron core is the same in the sense that theasynchronous components of the armature magnetomotive force become thecause of the eddy current loss of the magnets or the like. Therefore, itis needless to mention that with respect to the buried magnet typedynamo electric machine as well, the construction of this embodimentmode is adopted to thereby obtain the same effects.

[0074] In addition, while in this embodiment mode the inner rotor typedynamo electric machine has been described, it is needless to mentionthat even in the case of an outer rotor type dynamo electric machine inwhich a rotor is rotated along the outside of a stator, the same effectsare obtained. Moreover, it is needless to mention that not only in theradial gap type described in this embodiment mode, but also in an axialgap type in which a stator confronts with a rotor with respect to asurface perpendicular to a rotational axis, if a distance from therotational axis to rotor magnetic poles is defined as a radius of therotor, and a value which is double that radius is defined as a diameterD, the same effects are obtained.

EMBODIMENT 2

[0075] In this embodiment mode, similarly to the permanent magnet typedynamo electric machine shown in the embodiment mode 1, the descriptionwill hereinbelow be given with respect to an example in which such aconstruction as to meet Expression (19) shown in the above-mentionedembodiment 1 is applied to a permanent magnet type synchronous generatorfor wind power generation including a rotor having a plurality ofmagnetic poles composed of permanent magnets, and a stator havingarmature windings wound around the magnetic poles. Schematic diagrams ofa wind power generation system are shown in FIG. 11 and FIG. 12. Inthese figures, reference numeral 10 designates a tower as a pole braceof the wind power generation system, and reference numeral 11 designatesa nacelle provided on the tower 10. In the inside of the nacelle 11, inan example of FIG. 11, a generator 12 and an accelerating gear 13 areprovided, while in an example of FIG. 12, only the generator 12 isprovided. Reference numeral 14 designates a wind mill provided in a headof the nacelle 11, and reference numerals 15 and 16 designate a hub anda blade constituting the wind mill 14, respectively. Note that, therotor and stator are the same in construction as those of FIG. 1 shownin the above-mentioned embodiment 1, the description thereof is omittedhere.

[0076] As described above, in the example of FIG. 11, the nacelle 11 isprovided on the tower 10, the generator 12 and the accelerating gear 13are accommodated in the inside of the nacelle 11, and the wind mill 14is connected to the head of the nacelle 11. The wind mill 14 constitutedby the hub 15 and the blade 16, and the generator 12 are connected toeach other through the accelerating gear 13. In this system, since theaccelerating gear 13 is provided therebetween, whereby the rotationalfrequency of the generator 12 is made higher than that of the windmill14, there is an advantage in that a torque of the generator 12 may besmall, and hence the miniaturization of the generator 12 becomespossible. However, there are problems in noises generated by theaccelerating gear 13, maintenance of the accelerating gear 13, and thelike. On the other hand, in recent years, as shown in FIG. 12, aso-called gearless type wind power generation system in which the windmill 14 and the generator 12 are directly connected to each other isbecoming widespread. In the gearless type wind power generation systemconcerned, moreover, the permanent magnet type synchronous generator isadvantageous in a respect that there is no field system loss, ascompared with the winding field system type synchronous generator.

[0077] While in this system, there is no problem with respect to noisesdue to the accelerating gear, and maintenance, since a torque of thegenerator becomes larger than that of the gearless type, the physique ofthe generator itself becomes large. As has been described so far, inaccordance with Expression (18), the eddy current loss of the rotor isfurther increased as the rotor outer diameter D of the generator isincreased. Accordingly, if the selection of the number P of poles andthe number S of slots is not suitably carried out, then the eddy currentloss is increased and hence it is unable to make the best use of theadvantage of the permanent magnet type synchronous generator in whichthere is no field system loss.

[0078] Therefore, in the permanent magnet type synchronous generator forwind power generation, in particular, in the permanent magnet typesynchronous generator having a large rotor diameter that is incorporatedin the gearless type wind power generation system, such a constructionas to meet Expression (19) is adopted, whereby the eddy current loss ofthe rotor can be reduced to allow the calorification of the rotor to besuppressed, and at the same time, a high efficiency promotion of thegenerator can be realized. As a result, such an effect can be obtainedthat the energy of nature called a wind force can be effectivelyutilized.

EMBODIMENT 3

[0079] As has been described so far, in the large permanent magnet typegenerator or motor in which the rotor is of the concentrated wiring, ifthe number P of pole pairs and the spatial harmonic order N of themagnetomotive force to be the cause of an eddy current are not suitablyselected, then an eddy current loss of the rotor may be remarkablyincreased in some cases. In other words, if the number P of pole pairsand the number S of slots are not suitably selected, then there is afear of calorification due to the eddy current, and reduction of theefficiency. On the other hand, various combinations are considered forthe number 2 P of poles and the number S of slots of the dynamo electricmachine with the concentrated winding. As the combination which is oftenused, there are the combinations of 2 P:S=4:3, 10:9, 8:9, 10:12, 2:3 andthe like. Here, designs are considered of permanent magnet typesynchronous generators having the same output and each having a rotorouter diameter of 3 m under the condition of 64 poles and 48 slots, 60poles and 54 slots, 64 poles and 72 slots, 60 poles and 72 slots, and 64poles 96 slots so as for the number of poles to become about 60 withrespect to these five kinds of combinations. Note that, for the purposeof setting the same condition in order to make a comparison among theeddy current losses caused in the rotors, respectively, the rotationalfrequencies are made identical to one another. In addition, the widthsof slot opening portions were designed substantially equal to oneanother in order to prevent an influence of a change in permeance of aslot opening portion from being increased. Then, with respect to thesefive kinds of generators, eddy current losses caused in the rotorsduring the rated running were found on the basis of the analysis of theelectromagnetic field. The rates of the respective eddy current lossesto the outputs are shown in FIG. 13. From these results, it isunderstood that even if the numbers 2 P of poles are designedsubstantially equal to one another, there is a large difference in eddycurrent loss depending on the combination of the number of poles and thenumber of slots. Moreover, a graph in which the ratio S/2 P of thenumber of slots to the number of poles is plotted on the axis ofabscissa is shown in FIG. 14. From these results, it is understood thatwhen S/2 P>1, i.e., 2 P<S, the eddy current is small, conversely whenS/2 P<1, i.e., 2 P>S, the eddy current loss is large.

[0080] Let us consider the cause thereof. When paying attention to thespatial harmonic order N of the asynchronous components of themagnetomotive force to be the main cause of the eddy current withreference to FIG. 3 and FIGS. 5 to 8, in the combinations of 2 P S=4:3,and 10:9, i.e., 2 P >S, the asynchronous magnetomotive force componentseach having amplitude equal to or larger than that of the synchronouscomponent are present in the region having the asynchronous componentseach having a order lower than that of the synchronous component. Morespecifically, when 2 P:S=4:3, the magnetomotive force of −½-th order theamplitude of which is 2 times as large as that of the synchronouscomponent is present, and when 2 P:S=10:9, the magnetomotive force of−⅘-th order the amplitude of which is 1.25 times as large as that of thesynchronous component is present. However, in the combinations of 2P:S=8:9, 10:12, and2:3, i.e., 2 P<S, any of the asynchronousmagnetomotive force components each having large amplitude is absent inthe region having the asynchronous components each having a order lowerthan that of the synchronous component. In this case, since the numberof pole pairs is 30 or 32, i.e., is substantially fixed, and the rotorouter diameter D is also fixed, the magnitude of the eddy current lossof the rotor depends on the spatial harmonic order N of themagnetomotive force from Expression (18). Accordingly, when a largepermanent magnet type dynamo electric machine with concentrated windingis designed, it may safely be said that since when a relationship of 2P<S is adopted, N can be designed so as to be smaller, the eddy currentloss becomes less. Of course, even in the case of the condition of 2P>S, if the number of poles is increased to obtain such a constructionas to meet Expression (19), then the eddy current loss can be reduced.However, since if the values of the parameter X are intended to bedesigned so as to be identical to one another, then the number of polesis increased to increase the processing cost, which is disadvantageousas compared with the case where the condition of 2 P<S is adopted.

[0081] From the foregoing, in the large permanent magnet type dynamoelectric machine, such a construction as to meet the condition of 2 P<Sis adopted, whereby such an effect can be obtained that the eddy currentloss of the rotor can be reduced to allow the calorification of therotor to be suppressed, and at the same time, the high efficiencypromotion of the generator is realized. Moreover, in the case where aconstruction of reducing the eddy current loss is adopted, such aneffect can be obtained that it is possible to provide the permanentmagnet type dynamo electric machine which is less in processing cost andis lower in cost since the number of poles is decreased as compared withthe case where the condition of 2 P<S is adopted.

[0082] In particular, in the case where the dynamo electric machineswith the concentrated winding are designed with the numbers of polesbeing identical to or substantially identical to one another, since when2 P:S=2:3, N takes the largest value as compared with other cases, theconstruction can be made with the least number of poles, which is veryadvantageous. Since it is understood from FIG. 3 that since when 2P:S=2:3, the main cause of the eddy current is the opposite-phasemagnetomotive force of 2-nd order, in the case of 2 P poles, arelationship of N=2 P is obtained. When this relationship is substitutedfor Expression (19), the following Expression (20) is obtained:

P ^(0.5) D<1.85   (20).

[0083] Thus, such a construction as to meet Expression (20) is adoptedin the permanent magnet type dynamo electric machine with theconcentrated winding in which a combination of the number P of polepairs and the number S of slots has the ratio of 2 P:S=2:3, whereby anincrease in spatial harmonic order N of a specific higher harmoniccomponent of the armature magnetomotive force to be the cause of theeddy current can be especially realized with a small number of poles.Accordingly, such an effect can be obtained that the eddy current lossof the rotor can be reduced, and also such an effect can be obtainedthat the processing cost required for the magnetic poles can beespecially reduced.

[0084] On the other hand, a judgement is made similarly with respect tothe case as well where relationships of 2 P:S=8:9 and 10:12 areestablished even in the permanent magnet type dynamo electric machine ofthe concentrated wiring meeting the condition of 2 P<S. When therelationship of 2 P:S=8:9 is established, from FIG. 7, theopposite-phase magnetomotive force of 5/4-th order is the main cause ofthe eddy current. Then, N=5P/4 is substituted for Expression (19) toobtain the following Expression (21):

P ^(−0.5) D<0.43   (21)

[0085] Accordingly, when 2 P:S=8:9, such a construction as to meetExpression (21) is adopted, whereby such an effect can be obtained thatit is possible to provide a high efficiency permanent magnet type dynamoelectric machine in which the eddy current caused to flow through therotor is reduced to allow the calorification of the rotor to besuppressed. In addition, when 2 P:S=10:12, from FIG. 8, theopposite-phase magnetomotive force of 7/5-th order becomes a main causeof the eddy current. Then, N=7P/5is substituted for Expression (19) toobtain the following Expression (22):

P ^(−0.5) D<0.62   (22).

[0086] Accordingly, when 2 P:S=10:12, such a construction as to meetExpression (22) is adopted, whereby such an effect can be obtained thatit is possible to provide the high efficiency permanent magnet typedynamo electric machine in which the eddy current caused to flow throughthe rotor is reduced to allow the calorification of the rotor to besuppressed.

[0087] In addition, in the permanent magnet type dynamo electricmachines with the concentrated winding having the combinations of 2P:S=8:9 and 2 P:S=10:12, winding factors are 0.945 and 0.933,respectively, each of which is larger than 0.866 in the case of thecombinations of 2 P:S=4:3 and 2:3. Therefore, such an effect can beobtained that it is possible to provide a dynamo electric machine inwhich a quantity of use of the magnets can be reduced and which is lowin cost. In addition, in the case where the dynamo electric machines aredesigned with the numbers of poles being identical to or substantiallyidentical to one another, a least common multiple between the number ofpoles and the number of slots in this case becomes larger than that ofeach of the cases of 2 P:S=4:3 and 2:3. For example, in the cases of 64poles and 48 slots (2 P:S=4:3) and 64 poles and 96 slots (2 P:S=2:3),both the least common multiples are 192, whereas in the case of 64 polesand 72 slots (2 P:S=8:9), the least common multiple is 576, and in thecase of 60 poles and 72 slots (2 P:S=10:12), the least common multipleis 360. In general, a cogging torque is small as a least common multipleis larger. Accordingly, the combinations of 2 P:S=8:9 and 10:12 areadopted, whereby it is possible to obtain the permanent magnet typedynamo electric machine having a small cogging torque. In particular, inthe permanent magnet type synchronous generator for wind powergeneration, if a cogging torque is large, a wind velocity required toactivate a wind mill is increased, which is disadvantageous.Accordingly, the combinations of 2 P:S=8:9 and 10:12 are adopted,whereby a cogging torque becomes small, and as a result, such an effectcan be obtained that even if a wind velocity is low, a wind mill isactivated to allow a power generation to be started.

[0088] From foregoing, such a construction as to meet Expression (21) or(22) is adopted in the permanent magnet type dynamo electric machinewith the concentrated winding in which a combination of the number P ofpole pairs and the number S of slots has the ratio of 2 P:S=8:9 or10:12, respectively, whereby an increase in spatial harmonic order N ofa specific higher harmonic component of the armature magnetomotive forceto be the cause of the eddy current can be realized with the smallernumber of poles as compared with the case where the condition of 2 P>Sis adopted. Thus, such an effect can be obtained that the eddy currentloss of the rotor can be reduced, and also such an effect can beobtained that the processing cost required for the magnetic poles can beespecially reduced. Moreover, such an effect can be obtained that it ispossible to provide the dynamo electric machine, which is low in costsince the winding factor, is high to allow a quantity of use of themagnets to be reduced. In addition, such an effect can also be obtainedthat since a least common multiple between the number of poles and thenumber of slots is large, a small cogging torque is obtained and henceeven if a wind velocity is low, a wind mill is activated to start thepower generation.

EMBODIMENT 4

[0089] This embodiment mode is shown in FIG. 15. In this embodimentmode, a construction is adopted as shown in FIG. 15 in which, apermanent magnet 4 is fixed to a surface of a yoke 5 of a rotor, andalso the permanent magnet 4 is divided in an axial direction of therotor. The individual permanent magnets 4 obtained through the divisionare electrically insulated from one another. Since other constructionsare the same as those of the above-mentioned embodiment mode 1, thedescription thereof is omitted here.

[0090] In recent years, rare earth series magnets have been often used.However, since the rare earth magnet has high electric conductivity, aneddy current may become a problem in some cases. Then, as has beendescribed so far, the number P of pole pairs, the spatial harmonic orderN of the magnetomotive force and the outer diameter D of the rotor arecombined so as to meet Expression (19), and further, such a constructionis adopted that the permanent magnet 4 is divided as shown in FIG. 15,whereby the eddy current loss in the whole rotor can be reduced, and inaddition, the eddy current loss caused in the magnet itself can belargely reduced to allow the calorification of the permanent magnet 4 tobe suppressed. As a result, such an effect can be obtained that it ispossible to obtain the high efficiency permanent magnet type dynamoelectric machine.

[0091] The effects of the present invention will hereinafter bedescribed.

[0092] According to the present invention, there is provided a permanentmagnet type dynamo electric machine having a rotor having a plurality ofmagnetic poles composed of permanent magnets, and a stator havingarmature windings concentratedly wound around teeth, in which when thenumber of pole pairs of the magnetic poles of the rotor is P, a diameterof the rotor is D[m], a spatial harmonic order of a predetermined higherharmonic component of an armature magnetomotive force of the rotor is N(a mechanical angle 360 degrees is determined as 1-st order), and anoutput of the permanent magnet type dynamo electric machine is Pouts andthen the D is made equal to or larger than 0.00045 P_(out)+1.2, aparameter X (its unit is m) used to evaluate the rate of an eddy currentloss caused in the rotor is defined as follows;

X=(N+P)^(1.5) N ⁻⁴ P ² D

[0093] and values of the P, D and N are selected so that a value of theX becomes smaller than a predetermined value. Thus, such a constructionis adopted, whereby even if the permanent magnet type dynamo electricmachine is made large, it is possible to increase the specific spatialharmonic order N of the armature magnetomotive force to be the cause ofthe eddy current of the rotor and hence it is possible to reduce theeddy current generated in the rotor. As a result, such an effect can beobtained that the calorification of the rotor can be suppressed, and atthe same time, such an effect can also be obtained that the highefficiency promotion of the dynamo electric machine can be realized.Moreover, even if such a complicated and expensive construction asdescribed in the prior art is not adopted, where the yoke of the rotoris partitioned or insulatedly divided, such an effect can be obtainedthat the eddy current loss of the rotor can be reduced while keeping aconstruction having an integral one-piece yoke.

[0094] Further, according to the present invention, there is provided apermanent magnet type dynamo electric machine having a rotor having aplurality of magnetic poles composed of permanent magnets, and a statorhaving armature windings concentratedly wound around teeth, in whichwhen the number of pole pairs of the rotor is P, a diameter of the rotoris D[m], a spatial harmonic order of a predetermined higher harmoniccomponent of an armature magnetomotive force of the rotor is N (amechanical angle 360 degrees is determined as 1-st order), and an outputof the permanent magnet type dynamo electric machine is P_(out), andthen the D is made equal to or larger than 0.00045 P_(out)+1.2, the P, Dand N meet the following relationship:

(N+P)^(1.5) N ⁻⁴ P ² D<0.6

[0095] (its unit is m).

[0096] Thus, such a construction is adopted, whereby even if thepermanent magnet type dynamo electric machine is made large, it ispossible to increase the specific spatial harmonic order N of thearmature magnetomotive force to be the cause of the eddy current of therotor and hence it is possible to reduce the eddy current generated inthe rotor. As a result, such an effect can be obtained that thecalorification of the rotor can be suppressed, and at the same time,such an effect can also be obtained that the high efficiency promotionof the dynamo electric machine can be realized. Moreover, even if such acomplicated and expensive construction as described in the prior art isnot adopted, where the yoke of the rotor is partitioned or insulatedlydivided, such an effect can be obtained that the eddy current loss ofthe rotor can be reduced while keeping a construction having an integralone-piece yoke.

[0097] Further, when the number of slots of the stator is S, the P andthe S meet a relationship of 2 P<S. With such a construction, anincrease in spatial harmonic order N of the specific higher harmoniccomponent of the armature magnetomotive force to be the cause of theeddy current can be realized with a small number of poles as comparedwith a permanent magnet type dynamo electric machine in which 2 P>S.Thus, such an effect can be obtained that the eddy current loss of therotor can be reduced, and also such an effect can be obtained that theprocessing cost required for the magnetic poles can be reduced.

[0098] Further, when the number of slots of the stator is S, the P andthe S meet a relationship of 2 P:S=2:3, and also the P and the D meetthe following relationship:

P ^(−0.5) D<1.85

[0099] (its unit is m).

[0100] With such a construction, an increase in spatial harmonic order Nof the specific higher harmonic component of the armature magnetomotiveforce to be the cause of the eddy current can be realized with aparticularly small number of poles. Thus, such an effect can be obtainedthat the eddy current loss of the rotor can be reduced, and also such aneffect can be obtained that the processing cost required for themagnetic poles can be particularly reduced.

[0101] In addition, when the number of slots of the stator is S, such aconstruction is adopted that the P and the S meet a relationship of2P:S=8:9, and also the P and the D meet the following relationship:

P ^(−0.5) D<0.43

[0102] (its unit is m).

[0103] With such a construction, an increase in spatial harmonic order Nof the specific higher harmonic component of the armature magnetomotiveforce to be the cause of the eddy current can be realized with a smallnumber of poles. Thus, such an effect can be obtained that the eddycurrent loss of the rotor can be reduced, and also such an effect can beobtained that the processing cost required for the magnetic poles can bereduced. Moreover, since a least common multiple between the number ofpoles and the number of slots is large, such an effect can be obtainedthat a cogging torque can be reduced. Also, since a winding factor ishigh to allow a quantity of use of the magnets to be reduced, such aneffect can be obtained that the low cost promotion can be realized.

[0104] Further, when the number of slots of the stator is S, the P andthe S meet a relationship of 2 P:S=10:12, and also the P and the D meetthe following relationship:

[0105]P ^(−0.5) D<0.62

[0106] (its unit is m).

[0107] With such a construction, an increase in spatial harmonic order Nof the specific higher harmonic component of the armature magnetomotiveforce to be the cause of the eddy current can be realized with a smallnumber of poles. Thus, such an effect can be obtained that the eddycurrent loss of the rotor can be reduced, and also such an effect can beobtained that the eddy current loss of the rotor can be reduced.Moreover, since a least common multiple between the number of poles andthe number of slots is large, such an effect can be obtained that acogging torque can be reduced. Also, since a winding factor is high toallow a quantity of use of the magnets to be reduced, such an effect canbe obtained that the low cost promotion can be realized.

[0108] In addition, the above-mentioned permanent magnet constitutingthe magnetic poles of the rotor is axially divided to provide apartition construction, whereby it is possible to reduce the eddycurrent loss caused in the magnets. As a result, such an effect can beobtained that the calorification of the magnets can be suppressed, andhence it is possible to obtain the high efficiency permanent magnet typedynamo electric machine.

[0109] Moreover, according to the present invention, there is provided apermanent magnet type synchronous generator for wind power generationhaving a rotor having a plurality of magnetic poles composed ofpermanent magnets, and a stator having armature windings concentratedlywound around teeth, in which when the number of pole pairs of themagnetic poles of the rotor is P, a diameter of the rotor is D[m], aspatial harmonic order of a predetermined higher harmonic component ofan armature magnetomotive force of the rotor is N (a mechanical angle360 degrees is determined as 1-st order), and an output of the permanentmagnet type dynamo electric machine is P_(out), and then the D is madeequal to or larger than 0.00045 P_(out)+1.2, a parameter X (its unit ism) used to evaluate the value of an eddy current loss caused in therotor is defined as follows;

X=(N+P)^(1.5) N ⁻⁴ P ² D

[0110] and values of the P, D and N are selected so that a value of theX becomes smaller than a predetermined value. Thus, with such aconstruction, even in a large permanent magnet type synchronousgenerator having such a rotor diameter as to exceed 1 m which isincorporated in a permanent magnet type synchronous generator for windpower generation, in particular, in a gearless type wind powergeneration system, an eddy current loss caused in the rotor can bereduced, and as a result, the calorification of the rotor can besuppressed, and at the same time, the high efficiency promotion of thegenerator can be realized. Furthermore, even if such a complicated andexpensive construction as described in the prior art is not adopted,where a yoke of a rotor is partitioned or is insulatedly divided, suchan effect can be obtained that an eddy current loss of the rotor can bereduced while keeping a construction of an integral one-piece yoke.

[0111] Further, according to the present invention, there is provided apermanent magnet type synchronous generator for wind power generationhaving a plurality of magnetic poles composed of permanent magnets, anda stator having armature windings concentratedly wound around teeth, inwhich when the number of pole pairs of the rotor is P, a diameter of therotor is D[m], a spatial harmonic order of a predetermined higherharmonic component of an armature magnetomotive force of the rotor is N(a mechanical angle 360 degrees is determined as 1-st order), and anoutput of the permanent magnet type dynamo electric machine is P_(out),and then the D is made equal to or larger than 0.00045 P_(out)+1.2, theP, D and N meet the following relationship:

(N+P)^(1.5) N ⁻⁴ P ² D<0.6

[0112] (its unit is m).

[0113] Thus, with such a construction, even in a large permanent magnettype synchronous generator having such a rotor diameter as to exceed 1 mwhich is incorporated in a permanent magnet type synchronous generatorfor wind power generation, in particular, in a gearless type wind powergeneration system, an eddy current loss caused in the rotor can bereduced, and as a result, the calorification of the rotor can besuppressed, and at the same time, the high efficiency promotion of thegenerator can be realized. Furthermore, even if such a complicated andexpensive construction as described in the prior art is not adopted,where a yoke of a rotor is partitioned or is insulatedly divided, suchan effect can be obtained that an eddy current loss of the rotor can bereduced while keeping a construction of an integral one-piece yoke.

[0114] Industrial Applicability

[0115] As described above, the permanent magnet type dynamo electricmachine of the present invention is useful when being used in thevarious types of power generation such as wind power generation.

1. A permanent magnet type dynamo electric machine having: a rotorhaving a plurality of magnetic poles composed of permanent magnets; anda stator having armature windings concentratedly wound around teeth,characterized in that: when the number of pole pairs of the rotor is P,a diameter of the rotor is D[m], a spatial harmonic order of apredetermined harmonic component of an armature magnetomotive force ofthe rotor is N (a mechanical angle 360 degrees is decided as 1-storder), and an output of the permanent magnet type dynamo electricmachine is P_(out), and then the D is made equal to or larger than0.00045 P_(out)+1.2, a parameter X (its unit is m) used to evaluate therate of an :eddy current loss caused in the rotor is defined as follows;X=(N+P)^(1.5) N ⁻⁴ P ² D and values of the P, D and N are selected sothat a value of the x becomes smaller than a predetermined value:
 2. Apermanent magnet type dynamo electric machine having: a rotor having aplurality of magnetic poles composed of permanent magnets; and a statorhaving armature windings concentratedly wound around teeth,characterized in that: when the number of pole pairs of the rotor is P,a diameter of the rotor is D[m], a spatial harmonic order of apredetermined harmonic component of an armature magnetomotive force ofthe rotor is N (a mechanical angle 360 degrees is decided as 1-storder), and an output of the permanent magnet type dynamo electricmachine is P_(out), and then the D is made equal to or larger than0.00045 P_(out)+1.2, the P, D and N meet the following relationship:(N+P)^(1.5) N ⁻⁴ P ² D<0.6 (its unit is m).
 3. A permanent magnet typedynamo electric machine according to claim 1 or 2, characterized inthat: when the number of slots of the stator is S, the P and the S meeta relationship of 2 P<S.
 4. A permanent magnet type dynamo electricmachine according to any one of claims 1 to 3, characterized in that:when the number of slots of the stator is S, the P and the S meet arelationship of 2 P:S=2:3, and also the P and the D meet the followingrelationship: P ^(−0.5) D<1.85 (its unit is m).
 5. A permanent magnettype dynamo electric machine according to any one of claims 1 to 3,characterized in that: when the number of slots of the stator is S, theP and the S meet a relationship of 2 P:S=8:9, and also the P and the Dmeet the following relationship: P ^(−0.5) D<0.43 (its unit is m).
 6. Apermanent magnet type dynamo electric machine according to any one ofclaims 1 to 3, characterized in that: when the number of slots of thestator is S, the P and the S meet a relationship of 2 P:S=10:12, andalso the P and the D meet the following relationship: P ^(−0.5) D<0.62(its unit is m).
 7. A permanent magnet type dynamo electric machineaccording to any one of claims 1 to 6, characterized in that: thepermanent magnet constituting the magnetic poles of the rotor is axiallydivided to provide a partition construction.
 8. A permanent magnet typesynchronous generator for wind power generation having: a rotor having aplurality of magnetic poles composed of permanent magnets; and a statorhaving armature windings concentratedly wound around teeth,characterized in that: when the number of pole pairs of the rotor is P,a diameter of the rotor is D[m], a spatial harmonic order of apredetermined harmonic component of an armature magnetomotive force ofthe rotor is N (a mechanical angle 360 degrees is decided as 1-storder), and an output of the permanent magnet type dynamo electricmachine is Pout, and then the D is made equal to or larger than 0.00045P_(out)+1.2, a parameter X (its unit is m) used to evaluate the rate ofan eddy current loss caused in the rotor is defined as follows;X=(N+P)^(−1.5) N ⁻⁴ P ² D and values of the P, D and N are selected sothat a value of the X becomes smaller than a predetermined value.
 9. Apermanent magnet type synchronous generator for wind power generationhaving: a rotor having a plurality of magnetic poles composed ofpermanent magnets; and a stator having armature windings concentratedlywound around teeth, characterized in that: when the number of pole pairsof the rotor is P, a diameter of the rotor is D[m], a spatial harmonicorder of a predetermined harmonic component of an armature magnetomotiveforce of the rotor is N (a mechanical angle 360 degrees is decided as1-st order), and an output of the permanent magnet type dynamo electricmachine is P_(out), and then the D is made equal to or larger than0.00045 P_(out)+1.2, the P, D and N meet the following relationship:(N+P)^(−1.5) N ⁻⁴ P ² D<0.6 (its unit is m).